Abstract

CHAN CUPUL, Wilberth; HEREDIA ABARCA, Gabriela; RODRIGUEZ VAZQUEZ, Refugio  and  ARIAS MOTA, Rosa María. In vitro toxicity of the herbicides atrazine and paraquat on vegetative growth and sporulation of saprobic soil fungi. Rev. Int. Contam. Ambient [online]. 2014, vol.30, n.4, pp.393-406. ISSN 0188-4999.

The objective of this study was to assess the in vitro toxicity of the herbicides atrazine and paraquat on vegetative growth and sporulation of saprobic soil fungi. In thirteen strains of fungi isolated from soil, doses-response bioassays were performed with four concentrations of herbicides: atrazine (468, 937, 1875 and 3750 mg/L) and paraquat (93, 187, 375 and 750 mg/L). The fungi were inoculated with 2 μL of a spore suspension (1 x 10⁶ spores/mL) in Petri dishes with potato dextrose agar (PDA) supplemented with herbicides. Daily growth rates (DGR), percent inhibition of mycelial growth (% IMG), sporulation and the median effective concentration (EC₅₀) were evaluated. Paecilomyces carneus significantly showed the highest DGR (0.26 cm²/day) and maintained its sporulation rate (3.7 x 10⁵ spores/mL) at 468 and 937 mg/L of atrazine. The % IMG of P. carneus, P. marquandii and P lilacinus at 3750 mg/L of atrazine in APD were: 22.6 %, 44.4 % and 46.3 %; with an EC₅₀ of 6820 mg/L, 4736 mg/L and 3633 mg/L, respectively. Paraquat was more fungitoxic than atrazine; P. carneus significantly maintained its DGR (0.17 cm²/day) under 93 and 187 mg/L of paraquat. The EC50 of paraquat showed the lowest values compared to atrazine; Aspergillus tamarii obtained the highest EC₅₀ (256.4 mg/L) in paraquat. The genus Paecilomyces spp. and A. tamarii were the most tolerant to atrazine and paraquat, respectively. These strains are candidates to be included in studies regarding the biodegradation of both herbicides in environmental biotechnology.

Keywords : agrochemicals; dose-response; soil-fungus; mycobiota.

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